Molybdenite

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Molybdenite
Molly Hill molybdenite.JPG
Molybdenite on quartz from the Moly Hill Mine, Quebec, Canada
General and classification
chemical formula MoS 2
Mineral class
(and possibly department) 		Sulphides
System no. to Strunz
and to Dana 		2.EA.30 ( 8th edition : II / D.25)
02.12.10.01
Similar minerals graphite
Crystallographic Data
Crystal system hexagonal
Crystal class ; symbol dihexagonal-dipyramidal; 6 / m  2 / m  2 / m
Space group P 6 3 / mmc (No. 194)Template: room group / 194
Lattice parameters a  = 3.16  Å ; c  = 12.30 Å
Formula units Z  = 2
Physical Properties
Mohs hardness 1 to 1.5
Density (g / cm 3 ) measured: 4.62 to 4.73; calculated: 4.998
Cleavage completely after {0001}
Break ; Tenacity inelastic, flexible, mild
colour lead gray to blue violet
Line color dark gray to greenish gray
transparency opaque
shine Metallic luster
magnetism paramagnetic
Crystal optics
Pleochroism extreme reflective pleochroism
Other properties
Chemical behavior difficult to melt, hardly soluble in acids
Special features diamagnetic

Molybdenite , also known as molybdenum luster , eutom luster or water lead , is a frequently occurring mineral from the mineral class of " sulfides and sulfosalts ". It crystallizes in the hexagonal crystal system with the composition MoS 2 , so from a chemical point of view it is a molybdenum disulfide or molybdenum (IV) sulfide .

Molybdenite is mostly found in the form of crooked, scaly to massive aggregates from lead-gray to blue-violet in color, but rarely develops hexagonal, tabular crystals .

The rare element rhenium always occurs in low concentrations (from ppm to 1 to 2%) instead of molybdenum . In addition, there are often admixtures of silver and gold .

Etymology and history

Molybdenite was not named after its chemical constituent molybdenum, but after the Greek word μόλυβδος mólybdos or μόλιβος mólibos “ lead ”, which is already handed down in Mycenaean Greek as mo-ri-wo-do / moliu̯dos / .

classification

In the old systematics of minerals (8th edition) according to Strunz , molybdenite is still classified in the mineral class and division of "sulphides with the molar ratio metal (M): sulfur (S) (selenium, tellurium) <1: 1".

The mineral class remained the same in the new system of minerals (9th edition) . However, the minerals of this class have been partially redefined and the departments have been more finely divided. Since then, molybdenite has been in the department “Metal sulfides with M: S ≥ 1: 2” and the group “M: S = 1: 2; with Cu, Ag, Au, Ni, Sn, platinum group elements (PGE), Mo, W "

In the systematics of minerals according to Dana , molybdenite is in the section “Sulphides - Including Selenides and Tellurides where Am Bn Xp, with (m + n): p = 1: 2” (translation: Sulphide, Selenide and Telluride with Am Bn Xp and the molar ratio (m + n): p = 1: 2 , where A, B = cations and X = anions of the compound)

Crystal structure

Crystal structure of molybdenite

Two types of molybdenite are known to date :

The crystal structure of molybdenite is similar to that of graphite , but instead of the individual graphite layers, there are alternating layers of molybdenum and sulfur particles that can easily be moved against each other.

properties

Molybdenite is very similar in appearance and hardness to graphite , but differs from it in the line color , which is black to steel gray in graphite, but greenish gray to bluish gray in molybdenite. Molybdenite also feels greasy and stains.

The mineral has a Mohs hardness of 1 to 1.5 and a density of 4.7 to 4.8 g / cm 3 . It is usually opaque, but very thin flakes are translucent and see- through under infrared light.

Molybdenite is difficult to melt. In front of the soldering tube it is even infusible, but it colors the flame yellowish green ( siskin green ). The mineral is only sparingly soluble in acids.

Like graphite , molybdenite is a semiconductor and is diamagnetic .

Modifications and varieties

The MoS 2 compound is dimorphic and occurs naturally as an amorphous jordisite in addition to the hexagonally crystallizing molybdenite .

Education and Locations

Molybdenite crystal aggregate from Øvrebø ( Vennesla municipality ), Norway (size 5 cm)
Molybdenite (dark silver gray) - quartz (medium gray) - vein in alkaline granite (light colored areas) from the Climax Mine, Lake County (Colorado) , USA (width 5.3 cm at the base)

Molybdenite forms either in igneous rocks such as aplite , granite and pegmatite or through hydrothermal processes in highly thermal dike deposits and as impregnation in porphyry molybdenum deposits (“disseminated porphyry copper ores”). Accompanying minerals include chalcopyrite and other copper sulfides as well as fluorite , pyrite , quartz and scheelite .

Locations include Afghanistan ; several regions in Argentina ; many regions in Australia ; Brabant , Liège and Luxembourg in Belgium; Altenberg , Zinnwald and Ehrenfriedersdorf ( Ore Mountains ) in Germany; Horní Slavkov , Krupka and Štachlovice in the Czech Republic; Finland ; Traversella and Macchetto in Italy; several regions in Norway ; near Nerchinsk (Transbaikalia region) in Russia; Greenland ; many regions in Austria ; and many places in North America , e.g. B. Climax, Colorado .

use

Molybdenite is the most important ore for the extraction of molybdenum . Apart from the extremely rare rhenium , molybdenite is the only mineral with a worthwhile rhenium concentration , so that it is also the most important source of rhenium.

In addition to graphite , it is the most important mineral for the production of mineral lubricants ( solid lubricants ).

Since silicon and graphene were primarily known as transistor materials for microchips up to now , according to previous research results of a Swiss research group led by Andras Kis from the ETH Lausanne , molybdenite could also take on this task in the future. Similar to graphene, this should be able to be produced in only one atomic layer. With a layer thickness of only 0.65  nm , it should nevertheless have the same electron mobility as a silicon layer of 2 nm. In contrast, the energy efficiency should be even higher by a factor of 100,000. In contrast to graphs, in which the band gap required for semiconductors for switching a transistor on and off has to be artificially created, it is already present in molybdenite.

See also

literature

Web links

Commons : Molybdenite  - Collection of images, videos, and audio files

Individual evidence

  1. ↑ American Mineralogist Crystal Structure Database (English)
  2. ^ A b c Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  102 .
  3. ↑ a b c Molybdenite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 62.6 kB )
  4. ↑ a b Hans Jürgen Rösler: Textbook of Mineralogy . 5th edition. Spektrum Akademischer Verlag, Heidelberg 2002, ISBN 3-8274-1344-3 , p. 336 .
  5. ↑ Jörg Mildenberger: Anton Trutmann's 'Pharmacopoeia', Part II: Dictionary , Würzburg 1997 (= Würzburg medical-historical research, 56), Volume V, p. 2251f.
  6. ↑ Webmineral - Molybdenite (English)
  7. ↑ Martin Okrusch, Siegfried Matthes: Mineralogie: An introduction to special mineralogy, petrology and deposit science . 7th edition. Springer Verlag, Berlin 2005, ISBN 3-540-23812-3 , pp. 38 .
  8. ↑ Hans-Dieter Jakubke, Ruth Karcher (Ed.): Lexicon of Chemistry , Spectrum Academic Publishing House, Heidelberg, 2001.
  9. ↑ List of locations for molybdenite in the Mineralienatlas and Mindat
  10. ↑ Tec Channel - Molybdenite stands out from silicon and graphene; New transistor material for more efficient CPUs
  11. ↑ Energy & Technology - Swiss researchers prove silicon alternative; Molybdenite: transistor of the future?